In prior art semiconductor lasers, as typically disclosed in U.S. Pat. No. 5,172,384, entitled "Low Threshold Current Laser", issued Dec. 15, 1992, it is common to form an active region with an InGaAs quantum well, having spacing layers and cladding layers of AlGaAs on both sides thereof. Further, it is typical to form Bragg reflectors, or mirror stacks, on each side of the cladding layers, which mirror stacks generally include aluminum. The epitaxial configuration of VCSELs is well defined, however, various processing schemes can be utilized.
Short wavelength (below approximately 800 nm, and more specifically, 780 nm) vertical cavity surface emitting laser diodes (VCSEL) are of great interest in high density CD ROM applications. To obtain short wavelength emission in a GaAs system, and to maintain the lattice match to a GaAs substrate, the laser cavity should have AlGaAs as an active layer. However, the introduction of aluminum in the active region results in loss of lasing efficiency, since aluminum is highly reactive with oxygen, and oxygen behaves as a non-radiative recombination center in most III-V materials. The oxygen incorporation can occur either during the material growth or during device processing.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a short wavelength VCSEL with aluminum free active region.
Another object of the present invention is to provide a short wavelength VCSEL which has increased reliability and stability under high current injection and high temperature conditions.
Yet another object of the present invention is to provide a short wavelength VCSEL with a substantial reduction in the threshold current.
And another object of the present invention is to provide a short wavelength VCSEL inherently suitable for ridge-waveguide processing.